Proposed JRuby version can be optional

base-plugin/src/main/groovy/com/github/jrubygradle/JRubyExec.groovy

@@ -184,12 +184,12 @@ class JRubyExec extends JavaExec implements JRubyAwareTask, JRubyExecSpec {
     /** If it is required that a JRubyExec task needs to be executed with a different version of JRuby that the
      * globally configured one, it can be done by setting it here.
      *
-     * @deprecated Use{@code jruby.getJrubyVersion( )} instead.
+     * @deprecated Use{@code jruby.getProposedJRubyVersion( )} instead.
      *
      */
     @Deprecated
     String getJrubyVersion() {
-        deprecated('Use jruby.getJrubyVersion() rather getJrubyVersion()')
+        deprecated('Use jruby.getProposedJRubyVersion() rather getProposedJRubyVersion()')
         jruby.jrubyVersion
     }
 

base-plugin/src/main/groovy/com/github/jrubygradle/JRubyPluginExtension.groovy

@@ -111,7 +111,7 @@ class JRubyPluginExtension extends AbstractCombinedProjectTaskExtension {
      */
     @Deprecated
     String getDefaultVersion() {
-        deprecated('Use getJrubyVersion() rather than getDefaultVersion()')
+        deprecated('Use getProposedJRubyVersion() rather than getDefaultVersion()')
         getJrubyVersion()
     }
 

base-plugin/src/main/groovy/com/github/jrubygradle/JRubyPrepare.groovy

@@ -62,7 +62,7 @@ class JRubyPrepare extends AbstractJRubyPrepare {
      * @return Intended version of JRuby.
      */
     @Override
-    protected String getJrubyVersion() {
+    protected String getProposedJRubyVersion() {
         jruby.jrubyVersion
     }
 

base-plugin/src/test/groovy/com/github/jrubygradle/JRubyExecTaskSpec.groovy

@@ -72,12 +72,12 @@ class JRubyExecTaskSpec extends Specification {
         when:
         project.configure(execTask) {
             jruby.gemConfiguration configurationName
-            jruby.jrubyVersion newVersion
+            jruby.getProposedJRubyVersion newVersion
         }
         project.evaluate()
 
         then:
-        execTask.jruby.jrubyVersion != project.jruby.jrubyVersion
+        execTask.jruby.jrubyVersion != project.jruby.getProposedJRubyVersion
 
         and: "jrubyConfigurationName must point to this new configuration"
         execTask.jruby.getGemConfiguration().name == configurationName

core-plugin/src/main/groovy/com/github/jrubygradle/api/core/AbstractJRubyPrepare.groovy

@@ -110,10 +110,12 @@ abstract class AbstractJRubyPrepare extends DefaultTask implements JRubyAwareTas
      *
      * This method should not resolve any files to obtain the version.
      *
-     * @return Intended version of JRuby.
+     * @return Intended version of JRuby. Can be {@code null} if the version
+     * is indirectly inferred via configuration.
      */
     @Input
-    abstract protected String getJrubyVersion()
+    @Optional
+    abstract protected String getProposedJRubyVersion()
 
     @TaskAction
     void exec() {

gradle.properties

@@ -1,4 +1,4 @@
-version=2.0.0-alpha.5
+version=2.0.0-alpha.6
 group=com.github.jruby-gradle
 copyrightYear=2014-2019